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• Please explain some of Paul Graham's points on LISP

  - by kunjaan

  I need some help understanding some of the points from Paul Graham's article http://www.paulgraham.com/diff.html A new concept of variables. In Lisp, all variables are effectively pointers. Values are what have types, not variables, and assigning or binding variables means copying pointers, not what they point to. A symbol type. Symbols differ from strings in that you can test equality by comparing a pointer. A notation for code using trees of symbols. The whole language always available. There is no real distinction between read-time, compile-time, and runtime. You can compile or run code while reading, read or run code while compiling, and read or compile code at runtime. What do these points mean How are they different in languages like C or Java? Do any other languages other than LISP family languages have any of these constructs now?

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• ADO Entity Framework 4 to WPF Datagrid. DatagridComboBox nightmare.

  - by Jason

  The WPF datagrid -seems- like it's going to work, but the combobox implementation does not work straight from the designer. So I'm left wandering around in the XAML randomly changing things trying to get it to work. The problems are numerous. I want to display a foreign key relationship (with drop down) instead of a bunch of numbers for a selection. It seems like it shouldn't be this hard. I can get the right values to show up (their description instead of an ID), but the table freaks out thinking that all the values have been modified. If I select a drop down, it refuses to allow me to edit anything else. I want to chalk this up as a .NET bug, but since I'm new to WPF datagrids, it's probably just me. Here is the code. <DataGridComboBoxColumn Header="Make Up" ItemsSource="{Binding Source={StaticResource materialMakeUpTypesViewSource}}" DisplayMemberPath="Description" TextBinding="{Binding Path=MaterialMakeUpType.Description}" SelectedItemBinding="{Binding Path=MaterialMakeUpType.Description}" SelectedValueBinding="{Binding Path=MaterialMakeUpType.ID}" />

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• Design for a machine learning artificial intelligence framework

  - by Lirik

  This is a community wiki which aims to provide a good design for a machine learning/artificial intelligence framework (ML/AI framework). Please contribute to the design of a language-agnostic framework which would allow multiple ML/AI algorithms to be plugged into a single framework which: runs the algorithms with a user-specified data set. facilitates learning, qualification, and classification. allows users to easily plug in new algorithms. can aggregate or create an ensemble of the existing algorithms. can save/load the progress of the algorithm (i.e. save the network and weights of a neural network, save the tree of a decision tree, etc.). What is a good design for this sort of ML/AI framework?

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• self.navigationController is nil after adding subview

  - by Nnp

  here is my productscontroller.h ProductListViewController *productListViewController; ProductGridViewController *productGridViewController; UIButton *flipIndicatorButton; and i am adding list and gridview as a subview like this in my implementation ProductListViewController *listController = [[ProductListViewController alloc] initWithNibName:@"ProductListView" bundle:nil]; self.productListViewController = listController; self.productListViewController.CurrentSale = CurrentSale; [self.view insertSubview:listController.view atIndex:0]; but in when i tried to push detailview controller from ProductListViewController.m like this ProductDetailViewController *productDetailViewController = [[ProductDetailViewController alloc] init]; productDetailViewController.productIndexPath = indexPath; [self.navigationController pushViewController:productDetailViewController animated:YES]; it just does not work, then i check [self.navigationController] , it was nil, now how to deal with this problem. i am ready to give some more code and detail to make more clear. thanks

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• Cocoon lite / XML and XSLT publishing framework

  - by bambax

  What publishing frameworks (publishing only, NOT full-blown CMS) based on XML, XSLT sitemaps and pipelines exist, are stable, active, and simpler / lighter than Cocoon? I have glanced at: mod_xslt (http://www.mod-xslt2.com/) which seemed to be exactly that, but looks all but dead, and required a complex setup, and apparently supported only libxslt as an XSLT processor (I'd like to be able to use Saxon and XSLT 2.0 of course). Apache Forrest (http://forrest.apache.org/), but I don't understand if it is really simpler than Cocoon or is rather an additionnal thing on top of Cocoon? What I'm looking for is something that does just this: recieves an HTTP GET "runs it" through a sitemap finds a pipeline: source.xml - xslt1.xsl - xslt2.xsl - xsltn.xsl - serialize runs the pipeline serves the serialized result to the client and: uses Saxon (or is "processor independant") can be installed "lightly", that is: should not require much more configuration than the sitemap Maybe I'm describing an early version of Cocoon, or a future version of an XProc implementation... Anyway, does such a tool exist?

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• Best practice to calculate the average speed from GPS coordinates

  - by Sebi

  i have here a device which can give me gps coordinates. the time intervall i can define. i want to use it to calculate the average speed during driving or travelling by car. actually i used a orthodrome formula to calculate the distance between two points and then divided it by the given time intervall. by the implemenation i followed this term (http://de.wikipedia.org/wiki/Orthodrome#Genauere_Formel_zur_Abstandsberechnung_auf_der_Erde). Unfortunately i could only find a german link, but i think the formula should be understandable in any language ;) Unfortunately, using this formula and a time intverall of 1 seconds gives very unprecises results. the speed while walking is between 1 km/h and 20km/h. So i wonder if there is a general reference how to implement distance calculation between two gps coordinates (i found something similar on SO) and particulary, which is the best time intervall to update the GPS coordiantes.

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• Good examples of MVVM Template

  - by jwarzech

  I am currently working with the Microsoft MVVM template and find the lack of detailed examples frustrating. The included ContactBook example shows very little Command handling and the only other example I've found is from an MSDN Magazine article where the concepts are similar but uses a slightly different approach and still lack in any complexity. Are there any decent MVVM examples that at least show basic CRUD operations and dialog/content switching? Everyone's suggestions were really useful and I will start compiling a list of good resources Frameworks/Templates WPF Model-View-ViewModel Toolkit MVVM Light Toolkit Prism Caliburn Cinch Useful Articles Data Validation in .NET 3.5 Using a ViewModel to Provide Meaningful Validation Error Messages Action based ViewModel and Model validation Dialogs Command Bindings in MVVM More than just MVC for WPF MVVM + Mediator Example Application Additional Libraries WPF Disciples' improved Mediator Pattern implementation(I highly recommend this for applications that have more complex navigation)

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• How to calculate an angle from three points?

  - by HelloMoon

  Lets say you have this: P1 = (x=2, y=50) P2 = (x=9, y=40) P3 = (x=5, y=20) Assume that P1 is the center point of a circle. It is always the same. I want the angle that is made up by P2 and P3, or in other words the angle that is next to P1. The inner angle to be precise. It will be always a sharp angle, so less than -90 degrees. I thought: Man, that's simplest geometry maths. But I looked for a formula for like 6 hours now and people talk about most complicated NASA stuff like arcos and vector scalar product stuff. My head feels like in a fridge. Some math gurus here that think this is a simple problem? I think the programing language doesn't matter here but for those who think it does: java and objective-c. need that for both. haven't tagged it for these, though.

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• Why allow concatenation of string literals?

  - by Caspin

  I recently got bit by a subtle bug. char ** int2str = { "zero", // 0 "one", // 1 "two" // 2 "three",// 3 nullptr }; assert( values[1] == "one"_s ); // passes assert( values[2] == "two"_s ); // fails If you have godlike code review powers you'll notice I forgot the , after "two". After the considerable effort to find that bug I've got to ask why would anyone ever want this behavior? I can see how this might be useful for macro magic, but then why is this a "feature" in a modern language like python? Have you ever used string literal concatenation in production code?

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• Apache Camel ESB for C# and Java EDA

  - by Dokie

  Hi We are looking at integrating some of our coarse grained business Services using an Event Driven Architecture (EDA) and the server side of these Services (REST) are implemented in both Java and .NET (C#). We originally thought of using RabbitMQ (and AMQP protocol) as a neutral and open means (with good client support in these two languages), but it means having to support another runtime (Erlang) alongside Java and the CLR. We are also looking at Apache qPid as that has a Java broker implementation of the AMQP protocol which might eliminate that concern. Does anyone have any experience of trying to use the richer Apache Camel ESB on top of ActiveMQ to integrate Java and .NET Services in a Pub-Sub EDA manner? Have I missed any other possible suggestions as to a route through this? Thanks

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• How To Create An ASP.NET Designer Host

  - by Zuhaib

  I have been asked to build an application where I can drag and drop few WebControls onto the WebPage designer surface. So far I have read some articles on .NET Framework Design-Time architecture, like, MSDN Article: Hosting WinForms Designers, Developer Function Article etc. But I can't a find a way to host WebForms designer. The only open source implementation that I could find was Mono Develop ASP.NET Visual Designer. But in mono they have used GTK# & Gecko etc to host the designer. I can't find a way to do the same using WinForms. Please suggest me what should I do. Give me some pointers. Should I go ahead and implement it using GTK# and Gecko? PS: My requirement is not very huge. I need just a way to drag and drop simple web controls and save the page.

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• ExternalInterface in flex calling javascript function works for mozilla/chrome but NOT IE

  - by Rees

  hello, i have a flex application that does a simple ExternalInterface.call("shareOptions"), which calls a shareOptions() javascript method and works absolutely fine with Mozilla and chrome, however when I test with IE i get the following error: Error: [object Error] at flash.external::ExternalInterface$/_toAS() at flash.external::ExternalInterface$/call() I looked at the adobe livedocs documentation but can't determine what the issue is with IE. is there something i'm missing?? if anyone knows, please let me know ASAP! thanks in advance. private function shareOptions(event:MouseEvent):void{ ExternalInterface.marshallExceptions = true; if (ExternalInterface.available){ ExternalInterface.call("shareOptions"); } } the javascript <script language="JavaScript" type="text/javascript"> function shareOptions() { myWin = window.open('http://www.mysite.shareOptions.php','yeee!','width=640,height=690,toolbar=no,location=0,directories=no,status=no,menubar=no,scrollbars=no,copyhistory=no,resizable=yes,x=500,y=500'); myWin.moveTo(300,300); } </script>

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• Ruby on Rails vs Grails vs. Spring ROO vs. Spring App

  - by lizdev

  Hi, I'm planning on writing a simple web application that will be used by lots of users (as complicated as a simple bookmarking app) and I'm trying to decide which framework/language to use. I'm very experienced with Spring/Hibernate and Java in general but new to both Grails and RoR (and Spring ROO). The only reason I'm considering RoR is because Java hosting is MUCH more expensive than RoR hosting (which is supported by almost any hosting vendor for 5$ per month). Assuming the price wasn't an issue, which one of the frameworks/languages mentioned above would you recommend for a Java developer (who knows how to configure Spring/Hibernate etc.)? I'm afraid that by using RoR I won't be able to easily support many users who are using the website at the same time. thanks

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• How to write Haskell function to verify parentheses matching?

  - by Rizo

  I need to write a function par :: String -> Bool to verify if a given string with parentheses is matching using stack module. Ex: par "(((()[()])))" = True par "((]())" = False Here's my stack module implementation: module Stack (Stack, push, pop, top, empty, isEmpty) where data Stack a = Stk [a] deriving (Show) push :: a -> Stack a -> Stack a push x (Stk xs) = Stk (x:xs) pop :: Stack a -> Stack a pop (Stk (_:xs)) = Stk xs pop _ = error "Stack.pop: empty stack" top :: Stack a -> a top (Stk (x:_)) = x top _ = error "Stack.top: empty stack" empty :: Stack a empty = Stk [] isEmpty :: Stack a -> Bool isEmpty (Stk [])= True isEmpty (Stk _) = False So I need to implement a 'par' function that would test a string of parentheses and say if parentheses in it matches or not. How can I do that using a stack?

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• hta/ javascript How to execute an application with relative path

  - by user1644062

  I'm building a .hta (with javascript) from which i want to launch several applications. But when i execute my .hta i get the error message can't find file this is the code: <script type="text/javascript" language="javascript"> function RunFile(path) { var relpath = window.location.href; var fullpath = relpath + path; WshShell = new ActiveXObject("WScript.Shell"); WshShell.Run(fullpath, 1, false); } RunFile("\file.exe"); </script>

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• Help with a compiler warning: Initialization from distinct Objective-C type when types match

  - by Alex Gosselin

  Here is the function where I get the compiler warning, I can't seem to figure out what is causing it. Any help is appreciated. -(void)displaySelector{ //warning on the following line: InstanceSelectorViewController *controller = [[InstanceSelectorViewController alloc] initWithCreator:self]; [self.navController pushViewController:controller animated:YES]; [controller release]; } Interface and implementation for the initWithCreator: method -(InstanceSelectorViewController*)initWithCreator:(InstanceCreator*)creator; -(InstanceSelectorViewController*)initWithCreator:(InstanceCreator*)crt{ if (self = [self initWithNibName:@"InstanceSelectorViewController" bundle:nil]) { creator = crt; } return self; }

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• WCF <operation>Async methods not generated in proxy interface

  - by Charlie

  I want to use the Asnyc methods rather than the Begin on my WCF service client proxy because I'm updating WPF controls and need to make sure they're being updated from the UI thread. I could use the Dispatcher class to queue items for the UI thread but that's not what I'm asking about.. I've configured the service reference to generate the asynchronous operations, but it only generates the methods in proxy's implementation, not it's interface. The interface only contains syncronous and Begin methods. Why aren't these methods generated in the interface and is there a way to do this, or do I have to create a derived interface to manually add them?

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• Cross-platform embedded database/key-value store for C#

  - by Arne Claassen

  I'm looking for a fast, embeddable key/value store with cursor semantics over key collections (or a simple embeddable DB) that I can use in .NET and mono. Need it to be open-source, would prefer an MIT or Apache style license over a GPL license. Not opposed to a library that needs bindings to be written, as long as binaries are available for both windows and linux. Options considered: SQLite - has bindings and native implementation, but single-threaded and not all that fast Embedded InnoDB - no .NET bindings i can find and it's GPLv2 Berkley DB - no .NET bindings i can find Tokyo Cabinet - no .NET bindings i can find and problematic to build on windows MadCow Memory-mapped data structures - GPLv2 Is there an option better than the above that i'm missing, or bindings for the above i don't know about?

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• Weird "406 not acceptable" error

  - by Horace Loeb

  When I try to hit this action via Javascript, I get a 406 Not Acceptable error: def show @annotation = Annotation.find_by_id(params[:id]) respond_to do |format| format.html { if @annotation.blank? redirect_to root_path else redirect_to inline_annotation_path(@annotation) end } format.js { if params[:format] == "raw" render :text => @annotation.body.to_s else render :text => @annotation.body.to_html end } end end This is from jQuery, but I'm doing the right beforeSend stuff: $.ajaxSetup({ beforeSend: function(xhr) { xhr.setRequestHeader("Accept", "text/javascript"); }, cache: false }); Here are my request headers: Host localhost:3000 User-Agent Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 Accept text/javascript Accept-Language en-us,en;q=0.5 Accept-Encoding gzip,deflate Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive 300 Connection keep-alive X-Requested-With XMLHttpRequest Content-Type application/x-www-form-urlencoded

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• Why not port Linux kernel to Common Lisp?

  - by rplevy

  Conventional wisdom states that OS kernels must be written in C in order to achieve the necessary levels of performance. This has been the justification for not using more expressive high level languages. However, for a few years now implementations of Common Lisp such as SBCL have proven to be just as performant as C. What then are the arguments against redoing the kernel in a powerfully expressive language, namely Common Lisp? I don't think anyone (at least anyone who knows what they are talking about) could argue against the fact that the benefits in transparency and readability would be tremendous, not to mention all the things that can't be done in C that can be done in Lisp, but there may be implementation details that would make this a bad idea.

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• com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Unknown command

  - by adisembiring

  Hi .. I'm trying to create datasource for connection pooling mysql database in Websphere Application Server. I've set the JDBC Provider, I set the Implementation class name : com.mysql.jdbc.jdbc2.optional.MysqlConnectionPoolDataSource my mysql driver 5.1.6. but I got this error while I try to connect the datasource: The test connection operation failed for data source btn_itb_ds on server server1 at node qnode with the following exception: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Unknown command. View JVM logs for further details. I have read this http://bugs.mysql.com/bug.php?id=38388 trouble shooting. But they just suggest to upgrade mysql driver version 5.1.X and I have do that. but I've got the same error.

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• Implicit casting in VB.NET

  - by Shimmy

  The question is intended for lazy VB programmers. Please. In vb I can do and I won't get any errors. Example 1 Dim x As String = 5 Dim y As Integer = "5" Dim b As Boolean = "True" Example 2 Dim a As EnumType = 4 Dim v As Integer = EnumType.EnumValue Example 3 Private Sub ButtonClick(sender As Object, e As EventArgs) Dim btn As Button = sender End Sub Example 4 Private Sub ButtonClick(sender As Button, e As EventArgs) Dim data As Contact = sender.Tag End Sub If I surely know the expected runtime type, is this 'forbidden' to rely on the vb-language built-in casting? When can I rely? Thanks

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• Logging IP address for uniqueness without storing the IP address itself for privacy

  - by szabgab

  In a web application when logging some data I'd like to make sure I can identify data that came at differetn times but from the same IP address. On the other hand for privacy concerns as the data will be released publicly I'd like to make sure the actual IP cannot be retrieved. So I need some one way mapping of the IP addresses to some other strings that ensures 1-1 mapping. If I understand correctly then MD5, SHA1 or SHA256 could be a solution. I wonder if they are not too expensive in terms of processing needed? I'd be interested in any solution though if there is implementation in Perl that would be even better.

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• Identify in a unit test if Jetbrains IntelliJ IDEA 8 or 9 is running

  - by Ran Biron

  I need to know, in a context of a unit test, if Jetbrains IntelliJ idea is the test initiator and if it is, which version is running (or at least if it's "9" or earlier). I don't mind doing dirty tricks (reflection, filesystem, environment...) but I do need this to work "out-of-the-box" (without each developer having to setup something special). I've tried some reflection but couldn't find a unique identifier I could latch onto. Any idea? Oh - the language is Java.

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• Conversion of bytes into a type without changing the application (ie storing the conversion method i

  - by geoaxis

  Is there a way to store a conversion strategy (for converting some bytes) into a database and then execute it on the run time. If one were to store a complete java file, you would need to compile it, store the class and some how inject into the already running system. I am not sure how this would be possible. But using some kind of dynamic language on JVM would be nice. I see an example of execution of groovy from within spring context here http://www.devx.com/tips/Tip/42789 but this is still static in nature as application context contains the reference to the implementation and cannot be changed by database. Perhaps with JavaConfig of context it is possible. I am exploring options now, specifically with Spring 3.0. Your suggestions in any direction would be welcome.

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